Plant fossils are classified into two groups: (1)
macrofossils, which are the larger plant members, such as
stems and leaves, usually detached and often fragmented; and
(2) microfossils, which are the shells or resistant outer
walls of minute plants, such as diatoms, or of pollen grains
and spores. Fruits and seeds vary considerably in size and
overlap each group.

For several reasons pollen and spores have a particular
importance in present-day geological research in New Zealand.
(1) Being produced in large numbers, readily dispersed, and
highly resistant, they are more often preserved than
macrofossils. (2) They occur in sediments of terrestrial
origin where no marine fossils are available, often in
sufficient numbers for a comparison to be made of the
relative abundance of different types. (3) Since they are
also deposited in coastal waters and may be found associated
with marine organisms they help to “date” sedimentary rocks
in relation to marine fossil sequences.

Evidence of Climatic Change

Much of the evidence of climatic change depends on the
former occurrence of lowland trees north or south of their
present limits, the number of degrees in latitude giving some
indication of the magnitude of the climatic difference. Wood
and resin, indistinguishable from that of the living kauri,
occur in Tertiary lignites in Otago. These show that kauri
forests once grew much further south than their present
range, and indicate a warmer climate in the Tertiary. Kauri
pollen occurs in South Island Upper Miocene to Pliocene
deposits, and well-preserved leaves of Oligocene age have
been found at Landslip Hill, so that the southern extension
of the group to which the kauri belongs is shown by these
different fossils – wood, resin, leaves, and pollen. Cone
scales from Shag Point (Upper Cretaceous) and Mokoia and
Waikawa (Jurassic) show also that the kauri family has had a
long history in New Zealand.

Seasonal variation in climate may be shown by differences
in growth rings. These are clearly shown in Upper Jurassic
fossil woods from Waikawa, Curio Bay, and Waikato Heads.
Coniferous wood, which seems to have predominated in the
formation of the Tertiary lignites of the South Island, also
shows growth rings. (The Tertiary fossil woods, as well as
spores and leaf cuticles, are described by W. P. Evans in the
N.Z. Journal of Science and Technology, Vol. 9–19,
1928–37.)

Apart from numerous, but small and mostly unclassifiable
fragments of Mid-Devonian to Carboniferous age, Paleozoic
plant life is represented in New Zealand by plant fossils
from the Gore district. The fossils identified are of Permian
age and link New Zealand with the supposed ancient southern
continent, Gondwanaland, and in particular with Queensland
through the occurrence there and in New Zealand of
Cladophlebis roylei Arb. (a fern-like plant),
Sphenopteris lobifolia Morris (seed-fern), and
Neoggerathiopsis hislopii (Bunbury) (a cone-bearing
plant).

Links With Modern Ferns

One of the oldest plant microfossils so far named from New
Zealand deposits is Osmundacidites wellmani Couper.
This Jurassic spore is considered to be related to the living
family Osmundaceae, which is represented in New Zealand by
three species of Todea. The apparent link between
this ancient spore and the modern ferns is supported by other
evidence. Fossil stems known as Osmunda dunlopi
Kidston and Gwynne-Vaughan, from Waikawa and Kawhia
(Jurassic) are evidently closely related. These are of
interest on account of their anatomical similarity to modern
forms, and they show the extreme slowness with which the
family structure has been modified. According to Sinnott
(Annals of Botany, 1914) “there is perhaps no other
case among vascular plants where there has been so little
change from Mesozoic time to the present”. This stability
over a period of more than 135 million years is well
exemplified by our living Todea barbara (L.) Moore,
not only in stem anatomy but also in frond and spore
type.

Cladophlebis australis (Morris) is presumed also
to be the foliage of an osmundaceous fern. Hence there is a
plausible linkage between micro - and macrofossils which has
a bearing on the ancestry of certain present-day ferns. The
history of the Osmundaceae in New Zealand is extended by the
presence of Cladophlebis roylei among the Permian
plant fossils mentioned above. Of similar antiquity is
Cyathidites, a fern spore which may be ancestral to
the modern tree-fern genus Cyathea, the spores of
which are common in Quaternary deposits. The black tree fern
Cyathea medullaris (Forst. f.) Swartz, the finest of
our present-day tree-ferns, appears to be a comparative
newcomer in this ancient lineage, since the spores have not
been found in deposits older than Upper Miocene, though
common in younger deposits.

Character of Earlier Forests

Branchlets from Cretaceous and Eocene beds in the South
Island were identified as belonging to the genus
Casuarina, which contains the modern sheoaks of
Australia and Polynesia. Also believed to represent this
genus, and first appearing in the Upper Cretaceous, is
Triorites harrisii Couper, a pollen type which is
common in most Tertiary assemblages, but became extinct with
the onset of the Pleistocene glaciations. The presence of
Casuarina suggests that a forest of more open type
than today's dense rain forest was prevalent in the warmer
epochs of the Tertiary. Important groups in New Zealand
Tertiary vegetation were beeches, conifers, and
casuarinas.

The oldest dated deposits with the remains of angiosperms
(flowering plants with enclosed seeds) are the Mid-Cretaceous
beds in the Clarence valley, near Coverham. The pollen grains
are of an unspecialised type, but with the three furrows
which distinguish them as dicotyledonous. Of the three more
specialised pollen types of the southern beeches, two appear
during the Cretaceous and the third in the early Tertiary.
The first to appear, and the one which became dominant during
the Tertiary, represents a section of the genus
Nothofagus with living species in New Guinea and New
Caledonia, but now extinct in New Zealand. Fossil
Fagus (European beech) pollen has not been
identified in New Zealand as yet and, as it is of an
unspecialised type, confident identification is hardly to be
expected. Thus the linkage of the southern beeches, genus
Nothofagus, with the Northern Hemisphere beeches,
genus Fagus, remains obscure. As a possible “missing
link” may be mentioned the much discussed leaf fossils known
as Artocarpidium arberi Laurent of Upper Cretaceous
age from Pakawau. Oliver, in an unpublished manuscript,
points out the resemblance of the venation to that of
Fagus sylvatica and proposes a new genus for them,
Protofagus. Oliver also suggests an affinity of the
New Zealand leaf fossil Nothofagus ulmifolia Ett.
(Cretaceous) with the South American beeches, in particular
N. procera. Most of the fossil southern beeches had
larger leaves than the living New Zealand species. The leaf
fossil Nothofagus ninnisiana Unger from the Upper
Cretaceous (Shag Point) and Lower Tertiary (Waikato and Ohai)
is a broad-leaf type and fossil wood, believed to be that of
large-leaved beeches, was described by Evans in the articles
mentioned above. In the fossil record, as compared with the
four or five species now living, 23 species have been named
from macrofossils and 12 or 13 from microfossils, indicating
the variety and importance of the southern beeches in the
former vegetation of New Zealand and the closeness of
present-day New Zealand to the centre of evolution and
dispersal within this group.

Fruits and Seeds

Fossil fruits and seeds as yet yield a meagre record. At
Coopers Beach, Mangonui, and at one or two other localities
along the east coast, fossil coconuts of probable Miocene age
have been found. These were named Cocos zealandica
by Berry. The coconut fruits may have been brought by oceanic
drift, but in favour of a more local origin are the facts
that New Zealand may have consisted at the time of an
archipelago of small islands, and that large palm fronds have
been found at the same and other localities. Berry also
referred to another fruit resembling that of a species of the
Australian Hakea. Hakea-like pollen is known from
the Eocene of New Zealand. Seeds are more commonly preserved
in Quaternary sediments and may make a valuable contribution
to our knowledge of the Quaternary history of the flora. In
1953 D. R. McQueen described an assemblage of fossil seeds
from the Rangitikei Valley (Quaternary), of which 24 belonged
to living species. A concise summary of the history of the
flora of New Zealand was published by W. R. B. Oliver in a
Swedish journal (Svensk Botanisk Tidskrift, 1955),
and Oliver also contributed a similar article to
Tuatara (1950). A useful work on the conditions
under which the New Zealand flora evolved is New Zealand
Biogeography, by C. A. Fleming, in Tuatara
(1962). In the Transactions of the Royal Society of New
Zealand, Vol. 83, there are papers by Shona Bell, H. J.
Harrington and I. C. McKellar, and D. R. McQueen, and these
give further useful references to the literature on New
Zealand plant fossils. For plant micro-fossils the reader is
referred to N.Z. Geological Survey Paleontological
Bulletin 32 (1960), by R. A. Couper.

How to cite this page: 'PLANT FOSSILS – PALEOBOTANY', from An Encyclopaedia of New Zealand, edited by A. H. McLintock, originally published in 1966.Te Ara - the Encyclopedia of New ZealandURL: http://www.TeAra.govt.nz/en/1966/fossils/page-4 (accessed 26 May 2019)